Tropical Storm HENRI

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TROPICAL DEPRESSION HENRI DISCUSSION NUMBER 21
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT MON SEP 08 2003
THE GUILLOTINE HAS FALLEN ON HENRI. CONTINUOUS VERTICAL SHEAR OF
25-35 KT DURING THE LAST DAY OR TWO HAS WEAKENED ANY WELL-DEFINED
LOW-LEVEL CIRCULATION. IN ADDITION... THE NORTHWEST SIDE OF THE
CYCLONE IS BECOMING INCREASINGLY INVOLVED WITH A FRONTAL ZONE OVER
THE COASTAL WATERS OF THE SOUTHEAST UNITED STATES. SATELLITE
IMAGES SHOW COLD-AIR CUMULUS POURING INTO THE WESTERN SEMICIRCLE OF
HENRI...NOT AN ATTRIBUTE OF A TROPICAL CYCLONE. LARGE-SCALE
SATELLITE IMAGES SHOW A CLOUD PATTERN MORE LIKE AN EXTRATROPICAL
SYSTEM WITH A COMMA-LIKE APPEARANCE ON VISIBLE IMAGERY AND A WARM
FRONTAL FEATURE NORTHEAST OF HENRI. THUS... HENRI HAS LOST
TROPICAL CHARACTERISTICS. THERE IS SOME QUESTION ON WHETHER THIS
WEAK SYSTEM IS SUBTROPICAL... BUT THE APPEARANCE OF FRONTAL
FEATURES AND A RADIUS OF MAXIMUM WINDS OVER 100 MILES FROM THE
CENTER LEAD US TO CONCLUDE THAT IT IS INDEED EXTRATROPICAL.
INITIAL MOTION IS ESTIMATED AT 050/6 WITH A LOT OF UNCERTAINTY DUE
TO THE ELONGATION OF THE LOW-LEVEL CENTER FROM NORTHEAST TO
SOUTHWEST. THE GFS MODEL SHOWS THE SYSTEM SLOWLY MOVING TO THE
NORTHEAST FOR A COUPLE OF DAYS BEFORE A SHORTWAVE INDUCES WHAT
APPEARS TO BE A NEW LOW PRESSURE AREA ABOUT 300 MILES SOUTH-
SOUTHEAST OF MASSACHUSETTS. THE NHC TRACK IS JUST A BIT FASTER
THAN THE PREVIOUS ADVISORY IN REASONABLE AGREEMENT WITH THE GFS
MODEL.
FORECASTER BLAKE/PASCH
FORECAST POSITIONS AND MAX WINDS
INITIAL 08/2100Z 33.0N 75.0W 25 KT...BECOMING EXTRATROPICAL
12HR VT 09/0600Z 33.5N 74.0W 25 KT...EXTRATROPICAL
24HR VT 09/1800Z 34.0N 73.0W 25 KT...EXTRATROPICAL
36HR VT 10/0600Z 34.5N 72.0W 25 KT...EXTRATROPICAL
48HR VT 10/1800Z 35.0N 71.0W 25 KT...EXTRATROPICAL
72HR VT 11/1800Z 35.5N 70.0W 20 KT...DISSIPATING
96HR VT 12/1800Z...DISSIPATED
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